Publications by authors named "C Ulven"

Biocomposites can be both environmentally and economically beneficial: during their life cycle they generally use and generate less petroleum-based carbon, and when produced from the byproduct of another industry or recycled back to the manufacturing process, they will bring additional economic benefits through contributing to a circular economy. Here we investigate and compare the environmental performance of a biocomposite composed of a soybean oil-based resin (epoxidized sucrose soyate) and flax-based reinforcement using life cycle assessment (LCA) methodology. We evaluate the main environmental impacts that are generated during the production of the bio-based resin used in the biocomposite, as well as the biocomposite itself. We compare the life cycle impacts of the proposed biocomposite to a functionally similar petroleum-based resin and flax fiber reinforced composite, to identify tradeoffs between the environmental performance of the two products. We demonstrate that the bio-based resin (epoxidized sucrose soyate) compared to a conventional (bisphenol A-based) resin shows lower negative environmental impacts in most studied categories. When comparing the biocomposite to the fossil fuel derived composite, it is demonstrated that using epoxidized sucrose soyate versus a bisphenol A (BPA)-based epoxy resin can improve the environmental performance of the composite in most categories except eutrophication and ozone layer depletion. For future designs, considering an alternative cross-linker to facilitate the bond between the bio-based resin and the flax fiber, may help improve the overall environmental performance of the biocomposite. An uncertainty analysis was also performed to evaluate the effect of variation in LCA model inputs on the environmental results for both the biocomposite and composite. The findings show a better overall carbon footprint for the biocomposite compared to the BPA-based composite at almost all times, demonstrating a good potential for marketability especially in the presence of incentives or regulations that address reducing the carbon intensity of products. This analysis allowed us to pinpoint hotspots in the biocomposite's supply chain and recommend future modifications to improve the product's sustainability.

Wheat bran, abundant but underutilized, was investigated for its potential as a reinforcement in biocomposites through different pretreatment methods. Pretreatment methods included were dilute sodium hydroxide (NaOH), dilute sulfuric acid (HSO), liquid hot water (LHW), calcium hydroxide (CaOH), organosolv such as aqueous ethanol (EtOH), and methyl isobutyl ketone (MIBK). Changes in chemical composition and fiber characteristics of the treated bran were studied using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Cellulose content increased to 35.1% and 29.6% in brans treated with HSO and NaOH, respectively. The SEM micrographs showed surface cleaning of treated bran while maintaining sufficient surface roughness for the HSO, NaOH, and MIBK treated brans. Crystallinity index increased slightly for all treatments except HSO. NaOH and HSO pretreated brans achieved important fiber characteristics, which could be useful for making thermoplastic biocomposites. Innovative use of bran in thermoplastic will create more opportunities for growers while enhancing biodegradability.

In this study, six combinations of flax, hemp, and glass fiber were investigated for a hybrid reinforcement system in a polyurethane (PU) composite. The natural fibers were combined with glass fibers in a PU composite in order to achieve a better mechanical reinforcement in the composite material. The effect of fiber hybridization in PU composites was evaluated through physical and mechanical properties such as water absorption (WA), specific gravity (SG), coefficient of linear thermal expansion (CLTE), flexural and compression properties, and hardness. The mechanical properties of hybridized samples showed mixed trends compared to the unhybridized samples, but hybridization with glass fiber reduced water absorption by 37% and 43% for flax and hemp-agave PU composites respectively.

With the increase in structural applications of bio-based composites, the study of long-term creep behavior of these materials turns into a significant issue. Because of their bond type and structure, natural fibers and thermoset resins exhibit nonlinear viscoelastic behavior. Time-temperature superposition (TTS) provides a useful tool to overcome the challenge of the long time required to perform the tests. The TTS principle assumes that the effect of temperature and time are equivalent when considering the creep behavior, therefore creep tests performed at elevated temperatures may be converted to tests performed at longer times. In this study, flax fiber composites were processed with a novel liquid molding methacrylated epoxidized sucrose soyate (MESS) resin. Frequency scans of flax/MESS composites were obtained at different temperatures and storage modulus and loss modulus were recorded and the application of horizontal and vertical shift factors to these viscoelastic functions were studied. In addition, short-term strain creep at different temperatures was measured and curves were shifted with solely horizontal, and with both horizontal and vertical shift factors. The resulting master curves were compared with a 24-h creep test and two extrapolated creep models. The findings revealed that use of both horizontal and vertical shift factors will result in a smoother master curves for loss modulus and storage modulus, while use of only horizontal shift factors for creep data provides acceptable creep strain master curves. Based on the findings of this study, flax/MESS composites can be considered as thermorheologically complex materials.

Starch and cellulose are among the best known renewable reinforcing components. Scientists are continuously looking for various renewable sources such as flax, hemp, jute, and corn hulls with polymer matrixes to form composite materials and make structural biocomposites a reality. Wheat is a major cereal grain in the US and the world. During wheat milling, a large amount of wheat bran, a by-product, is disposed off as waste. The high percentage of water-insoluble fiber in wheat bran could be advantageous for reinforcing industrial material. However, the utilization of cellulosic fibers derived from wheat byproduct has not been explored in processing of biocomposites. Therefore, the objectives of this study were to characterize wheat bran fiber compositions including dry matter (DM), ash, crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose (Cell), hemicellulose (Hemi), calcium (Ca), fat, starch, and acid detergent lignin (ADL); identify the interrelationship between the fiber composition traits and the influence of the environment and genotype on these traits. The experiment included six diverse and popular hard red spring wheat (HRSW) cultivars commonly grown in spring wheat region of the Northern Plains of USA. The experiment was installed in three different environments in the Dakotas States, USA. Results from this study showed that the DM, ash, Ca, Cell, starch, and ADL contents were influenced mainly by environments. However, CP along with fat, ash and Ca contents were influenced by genotypes in addition to environment. All bran components were influenced by the genotype × environment (G × E) interactions. We observed significant negative correlation of Cell with CP and ADL which make wheat bran a suitable reinforcing industrial material. However surface treatment of bran fiber would make it even more efficient. These preliminary results indicate the potential use of wheat bran components as biocomposite, but further studies to elucidate more these finding are warranted.